PROJECT SUMMARY/ ABSTRACT Despite the success of combined antiretroviral therapy (cART) to diminish peripheral infection, HIV-1 can establish an infection in the central nervous system (CNS), resulting in the development of cognitive, behavioral, and motor deficits associated with HIV-1 associated neurocognitive disorders (HAND). Once infected, the CNS acts as a viral reservoir that is difficult to treat and eradicate. Mononuclear phagocytes (MP, e.g., perivascular macrophages and microglia) are important reservoirs in the immune-privileged CNS. The proposed studies are designed to address the unique dynamics of HIV infection in CNS and explore novel therapeutic strategies that target MP, ensure viable delivery across the blood-brain barrier (BBB) to eliminate the HIV reservoir and reduce inflammation. HIV-induced activation and viral replication in MP are relevant targets that that are the focus of our ongoing novel approaches through multiple pharmacological agents. These approaches include design and development of: 1) MP-specific ribonucleoside chain terminators (rNCTs) and their phosphate prodrugs, and 2) NADPH oxidase (NOX) inhibitors that cross the BBB and target MP, and 3) JAK inhibitors that block/interrupt the activation state of MP and can reduce inflammation. Selected therapeutic agents will be analyzed for their in vitro antiviral potency, and to assess biochemistry, toxicology, and cellular pharmacology parameters. We have recently identified low or sub-nanomolar MP-specific HIV inhibitors with a high therapeutic index. These will be evaluated in vivo to assess CNS pharmacology and response (including behavior and pathology) to treatment using two distinct retrovirus CNS animal models we have previously established including SCID mouse model intracranially injected with HIV-1 infected MP, and macaque model infected with SIVmac239. Results from these studies will identify new adjunctive therapeutic strategies which together with current cART should provide improved targeted therapy to MP. The ultimate goal is to suppress virus and eliminate these HIV- 1 reservoirs in the CNS that should lead to improved treatments to reduce risk(s) of developing HAND.